Various electronic devices are mounted on a vehicle as transportation. The vehicle is equipped with a wire harness that is used to transmit power from a power supply or control signals from a control device to the electronic devices.
The wire harness includes a wire and a connector. The wire includes a core wire which is obtained by twisting thin wires, and an insulation coating which is formed of an insulating synthetic resin and covers the outer periphery of the core wire. The connector includes a housing which is formed of an insulating synthetic resin, and a terminal fitting which is received inside the housing and is attached to the terminal end of the wire.
In general, copper is used as a material of the core wire used in the wire harness. However, in recent years, there has been a strong demand for a reduction in the weight or an improvement in recyclability of the vehicle in accordance with increasing ecological awareness. For this reason, aluminum or aluminum alloy having a specific weight that is ⅓ of copper and has excellent recyclability has been more widely used as the core wire of the harness. Further, Patent Document 1 discloses a terminal fitting that is attached to a wire harness having a core wire made of aluminum or aluminum alloy.
The terminal fitting proposed by Patent Document 1 is shown in FIG. 8. A terminal fitting 701 includes a terminal contact portion 710 and a wire connection portion 720. The terminal contact portion 710 is formed in a rectangular cylindrical shape, and has a spring piece therein. Further, the wire connection portion 720 includes a wire barrel 721 which press-bonds a core wire 741 of a wire 740, and an insulation barrel 722 which press-bonds the wire 740 from above an insulation coating 742.
The wire barrel 721 is formed to have a fork structure of which the heights of the front and rear portions are different from each other. That is, the wire barrel 721 includes a first wire barrel 721a which is adjacent to the insulation barrel 722, and a second wire barrel 721b which is lower than the first wire barrel 721a. 
The wire 740 press-bonded by the wire barrel 721 includes a core wire 741 which is obtained by twisting thin wires made of aluminum or aluminum alloy, and an insulation coating 742 which is formed of an insulating synthetic resin and covers the outer periphery of the core wire 741, where the core wire 741 is exposed by removing the insulation coating 742 by a predetermined length from the end portion of the wire 740. The exposed core wire 741 includes a first conductor portion which is adjacent to the insulation coating 742 and has a predetermined length and a large diameter, and a second conductor portion which is adjacent to the first conductor portion, is obtained by removing thin wires located at the outer peripheral surface of the first conductor portion, and has a predetermined length and a small diameter.
Then, the first wire barrel 721a of the terminal fitting 701 is crimped to be press-bonded to the first conductor portion of the wire, and the second wire barrel 721b of the terminal fitting 701 is crimped to be press-bonded to the second conductor portion of the wire, thereby connecting the terminal fitting 701 to the core wire 741 of the wire 740. Further, the insulation barrel 722 of the terminal fitting 701 is crimped to be press-bonded to the insulation coating 742 of the wire 740, so that the terminal fitting 701 is fixed to the insulation coating 742 of the wire 740. Then, according to the terminal fitting 701, as shown in FIGS. 9 and 10, the respective thin wires of the wire 740 may be made to contact the terminal fitting 701 and maintain a reliable electric connection.